Self-adjusting cutter bar for lawn mowers



y ,1935; A. D. BUNN 2,007,743

SELF ADJUSTING CUTTER BAR FOR LAWN MOWERS Filed oct. 27, 19:3 2 Sheets-Sheet 1 I n-uentmf Atto'mgy July 9, 1935. A, BUNN 2,007,743

SELF ADJUSTING CUTTER BAR FOR LAWN MOWERS Filed Oct. 27'. 1935 2 Sheets-Sheet 2 Patented Jul 9, i935 x r 2,007,743

I I L 2,007,743 i SELF+ADJUSTING CUTTER BAR FOR LAWN MOWERS Arthur D Bunn, SavannaQOkIa. Application cto'ber'27, 1933, Serial-No. 6955M I g I i claimflwi. 56494) I '.''This invention "relates to an improved cutter mediate portion thereof isa reinforcing plate 1 bar for lawn mowers of a motor driven type,.as secured by rivets or the like 3, this being ofap- Well as the ordinary walking attendant pushed priate proportions and shape to afford the desired and steered style generally used for home or degree of rigidity and at the same'time permit :5, domestic purposes. r Y the requisite resilient properties. In opposite :5 Stated otherwise, ,the invention is'xprimarily ends of the bar are pivot boltsaappropriately adapted to a't-Wo wheeled'lawn mowerof the form secured to the lawn mower frame structure. embodying a rotary driven bladed reel or rotor These serve as supports for hanger units for the wherein the spiral blades swingsuccessively into bar 5. These units arehere shown as of right shearingand metallic sharpeningcontact with a angular form and differentiated by'the numeral horizontal bar mounted on the framein the path 563.. The vertical flanges thereof are apertured "ofrotation iofsaid blades. I 1 i and mounted for oscillation on the pivot pins '9.

In carrying the principles of the present in- As shown in Figure 3,the pivotal connections for ventive conception 'into actual practice; I have these suspension or hanger-brackets H! are such 15. evolved and produced a notvfel and practicable bar as to allow'the iearlongitudinal edge portion of '15 construction andlmo'unting wherein said bar is the bar to be 'tilted rearwardly anddownwardly. suspended for oscillation in a limited arc and is Incidently, and under certain conditions, these itself made of flexible steel susceptible of flexing brackets I0 are provided with rearwardly projectin a manner to be self-accommodating and ading arm-like extensions II which, as shown in justing and. to thereby attain the desired features Figure 3, have their extreme rear ends inclined 20 of shape, conformation and adaptation believed downwardly at 2 to terminate in ground engagto be more satisfactory in promoting severing of ing feet i3.v These features H, l2 and I3 form the grass and self-sharpening of the blades of the what may be designated as a trip device. There reel. is a device at each, end of the bar 6 and the rear In selecting a structure capable of accomplishterminal or foot I3 is swingable in the direction 25 ing these results, I have provided an arrangeof the arrows A and when it swings upwardly, it ment which is believed to be scientifically and tilts the shearing edge of the bar ii, downwardly mechanically correct, appropriately balanced, in the direction of the arrow B and away from aptly fitted for the purposes intended and charthe blades of the reel or rotor M. In the acterized by features of accommodations and ordinary conventional type of lawn mower having 30 adaptation which transcend those of similar the rearwardly extending handle bar, it is obvious known arrangements. that when said handle bar is released, the feet Other features and advantages will become I3 drop down into contact with the ground, thus more readily apparent from the following deswinging the shearing edge of the bar 6 away scription and the accompanying, illustrative from the cutting blades so as to provide a de- 35 drawings, Y sired degree of clearance. This is particularly In the drawings, wherein like numerals are useful in electric motor driven types of lawn employed to designate like parts throughout the mowers in that it permitsfree rotation of the views': bladed rotor when the motor is started and before 40 Figure 1 is a front elevational view of the the handle bar (not shown) is lifted to steer the 40 assembly, showing the manner in which it is atlawn mower.

tached to the lawn mower frame or support. The means for automatically adjusting the bar Figure 2 is a top 'plan view of the assembly 6 into the path of movement of the rotating blade shown in Figure 1. is of an automatic type. The preferred embodi- Figure 3 is a transverse or cross sectional view. ment thereof comprises spring devices of a dupli- 45 Figure 4 is a detail perspective view. catetypemounted on the frame at opposite ends Figure 5discloses a view showing the cutter bar of the bar. Each device comprises a supporting attached to a lawn mower. fixture. This is here shown as in the form of an Referring now to the drawings by detailing eye bolt Whose shank i5 is attached to the frame 5 and distinguishing reference characters," it will and whose eye Iii serves as a guide and support be observed that the numeral 5 designates like for a bolt H. The headed end of the bolt is conportions of a conventional lawn mower (not inected with one end portion of the bar 6 at a shown). The cutter bar per se is denoted by the point rearwardly f t PiVOtal Suspension of Said numeral 6 and comprises a rectangular plate or bar, as shown in Figure 3. The upper threaded strip 'of pliant steel. Attached to the interend l8is provided with an adjusting and retaining 55 V nut l9 and the numerals 20 merely designate guide and stabilizing washers. The numeral 2| designates a coiled spring which surrounds the shank of the bolt between the end portion of the bar and the bolt supporting fixture. The spring can be tensioned as conditions require to permit the sensitivity of control to be adequately regulated.

The gist of the invention is found in the provision of a suitably reinforced flexible steel bar 6 having its end portions mounted for oscillation on the frame of a lawn mower, together with adjustable spring pressed means on said frame 00- operable with the rear longitudinal edge portion of the bar to bring about the desired tilting action and to tilt the shearing front edge of the bar into sharpening and shearing contact with the blades of the rotor. This spring pressed arrangement renders the bar 6 substantially self-accommodating and adjusting with respect to the cutting blade. Not only this, the flexible properties of the bar itself are suchas to permit it to present the'desired inherent resilient characteristics, allowing it to twist transversely and to allow it to conform in shape to the progressive feed-in action of the spiral cutting blades. It is to be remembered that the entire cutting edge of the blade does not come into contact with the bar at once, but gradually feeds into contact and the resiliency of the bar 6 allows said bar to shape itself to the pressure developed against it by the incoming blade. This double oscillation and twist result provides for-the requisite compensating action necessary. It is'partieularly advantageous in an arrangement of this kind-wherein the blades are progressively or successively brought into shearing and sharpening contact with the bar 6.

Emphasis is also placed on the extension arms I l which constitute trip devices to overcome the tension of the springs and to swing the shearing edge of the plate or bar downwardly in the direction of the arrows A, as shown in Figure 3, to provide for clearance when said clearance is needed. When these arms II are used, it is generally advisable to omit the usual ground engaging roller (not shown) found on conventional lawn mowers.

It is thought that the description, taken in connection with the drawings, will enable a clear understanding of the invention to be had. Therefore, a more lengthy description is thought unnecessary. I 7

While the preferred embodiment of the invention has been shown and described, it is to be understood that minor changes coming within the field of invention claimed may be resorted to if desired.

I claim:

In a cutter bar attachment for lawn mowers having a frameand a rotary cutting member, a cutter bar pivoted to said frame rearwardly of the rotary cutting member, yieldable means carried by said frame and connected to said cutter bar rearwardly of the pivot therefor for urging said cutter bar into engagement with the rotary cutting member, and an extension carried by and projecting rearwardly and downwardly from the cutter bar and adapted to be engageable with the ground for moving the cutter bar out of contact with the rotary cutting member.

ARTHUR D. BUNN. 

